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Table 3 Susceptibility of P. aeruginosa biofilms to various treatments after 3 and 60 days of growth, determined by disk diffusion

From: Antibacterial activity of iron oxide, iron nitride, and tobramycin conjugated nanoparticles against Pseudomonas aeruginosa biofilms

Material

Dose on disk (μg)

ZOI (mm)

day 3

ZOI (mm)

day 60

Fe3O4 NPs†

10

22/S

21/S

5

17.5/S

16/S

2.5

11/R

10/R

Fe3O4@PEG NPs

10

0/R

0/R

5

0/R

0/R

2.5

0/R

0/R

Fe3O4@ALG NPs

10

22/S

22/S

5

16/S

15/S

2.5

10/R

8/R

Fe3O4@ALG:TOBRA NPs

10

23/S

22/S

5

11/R

15/I

2.5

7/R

5/R

ZVFe@ALG NPs

10

25/S

24/S

5

21/S

22/S

2.5

20/S

20/S

Tobramycin

10*

10/R

0/R

100**

25/R**

15/R**

1000**

35/R**

32/R**

  1. Interpretation: R resistant, I bintermediate, S susceptible, ZOI zone of inhibition, PEG polyethylene glycol, ALG alginate, TOBRA tobramycin, ZVFe zero-valent iron
  2. †Uncapped NPs. *CLSI breakpoint for susceptibility of tobramycin by disk diffusion is 10 μg. Therefore, all colonies are found to be tobramycin resistant by CLSI standards. **Higher tobramycin doses in the disk were investigated to determine whether any susceptibility existed at higher doses. At present, there are no CLSI values/breakpoints for NPs as antimicrobial agents